Multicylinder refrigerant compressing apparatus



April 24, 1951 v w, DODSON 2,550,457

.MULTICYLINDER REFRIGERANT COMPRESSING APPARATUS Filed Dec. 21, 1949 Inventor: Wayne E. Dodson,

His Attor'n ey.

Patented Apr. 24, 1951 MULTICYIiINDER, REFRIGERANT COMPRESSING APPARATUS Wayne E.,Dodson, Caldwell, N. J., assignor to General Electric Company, a corporation of New York Application December 21, 1949, Serial No. 134,249

My invention relates to refrigerant compressing apparatus havingtwo or more compression cylindersg'and particularly to such apparatus wherein the capacity may be varied by by-passing one or more-of the cylinders.

Inrefrigerating apparatus it is frequently desirable to provide some arrangement for changing the effective capacity-of the compressor. In some installations it is desirable that changes in capacity may be eifected without changing substantially the average speed of the compressor, and one/method for accomplishing this purpose is to return-to the suction line the refrigerant gas compressed in one or more of the cylinders. Accordingly itis an object of my invention to provide 2 Claims. (01. 230-2) a multicylinder;compressing apparatus having.

provision for by-passing one or more of the cylinders and including an improved arrangement for minimizing the heating of the by-passed cylinders by. recirculation of compressed refrigerant.

Further objects and advantages of my invention 'will become apparent as the following description proceeds, and'the features of novelty which characterize my invention will be pointed out-"with.;particularity in the claims annexed to and forming a part of this specification.

In :carrying outthe objects of my invention, I provide a compressing apparatus in which one or more of the cylinders is arranged to be bypassed so that the refrigerant pumped therein is returned to thesuction line. The discharge connection from the by-passed cylinder is arranged to-convey the pumped refrigerant directly to the intake of an active cylinder sothat the gas discharged'irom the by-passed' cylinder enters the active cylinder rather than being recirculated through the by-passed 1 cylinder, which would thereby be subject to excessive heating.

For a better understanding of my invention, reference may be had to the accompanying drawing, the single figure of which represents diagrammatically an air cooling system provided with a refrigerating machine embodying my invention.

Referring now to the drawing, air circulated by a suitable blower (not shown) passes through a duct over the coils of an evaporator H. The evaporator is supplied with liquid refrigerant from a liquid receiver l2 through a liquid line [3 under control of a suitable refrigerant flowcontrol device, such as a thermostatic expansion valve Hi, this valve having a temperature responsive element I5 secured in heat exchange with the outlet of the evaporator ll. Refrigerant vaporized in the evaporator by absorption of heat from the air flowing through the duct I0 is removed through a suction line i6 by operation of a compressing apparatus ll. The apparatus 1-! comprises two cylinders i8 and I9 which are driven by the same motor (not shown) and comprise a multicylinder compressor. Suction line I6 is connected to the intakes of the cylinders I8 and :9 by conduits and 2| respectively, and the refrigerant compressed in the cylinders l8 and I9 is delivered through discharge conduits 22 and .23 respectively to a condenser 24. The hot compressed refrigerant in the condenser 24 is cooled by heat exchange with air, water or other suitable cooling fluid circulated over the surface of the condenser by suitable pumps or blowers (not shown), and the refrigerant liquefied in the condenser then flows by gravity to the liquid-receiver l2.

When the load demand on the, compressor H has been reduced during the cooling operation, it may be desirable to continue the operation of the compressor at reduced capacity, and in order to effect a reduction in capacity the discharge conduit 23 of the cylinder 19 is arranged to be connected to the suction line through a conduit 25 having a normally closed solenoid valve 26 therein. The demand for reduced loading may be determined, for example, by reduction in the suction pressure below a predetermined value, anda bellows 27 is connected through a duct 28 to the suction line for this purpose. When the suction pressure falls to a predetermined value, the bellows 21 contracts sufficiently to move a link 29 on a switch mechanism 30 over the center line of a spring 3| so that the spring moves a switch arm 32 into engagement with a contact 33. This connects a solenoid 34 of the valve 26 to electric power lines '35, the solenoid being connected to one side of the lines 35 and the switch arm 32 being connected to the other side through a line 35. When the solenoid 26 is opened, refrigerant compressed in the cylinder [9 is discharged di, rectly through the conduit 25 to a suction connection 3? of the cylinder l8, this being the connection to which the suction conduit 20 is also connected. Return of compressed refrigerant to the cylinder it through the conduit 23 i prevented by a check valve 38. Thus when thevalve 26 is opened, refrigerant pumped by the'cylinder Isis returned directly to the suction or low pressure side of the system and the cylinder is thus unloaded.

Refrigerant vaporized in the evaporator ll flows to both cylinders l8 and Hi from the suction line It; however. because the discharge or bypass conduit conduct refrigerant from the cylinder [9 directly to the intake connection 31 of the cylinder 18, the cylinder l8 receives the heated refrigerant from the cylinder l9 while the cylinder l9 receives substantially only the cool refrigerant from the suction line 5., In order to make sure that substantially all the gas discharged from the by-passed cylinder l9 enters the cylinder I8, the pistons of the two cylinders, as indicated by dotted lines on the drawing at 39 and 46 respectively, are arranged to be driven so that the intake portion of the cycle of the cylinder l8 occurs during the discharge portion of the cycle of the cylinder 49. The cylinders l8 and I9 may, for example; be only two cylinders of a compressor having four or more cylinders, and obviously the by-passed cylinders may each be arranged to discharge bypassed refrigerant to a working cylinder having its intake stroke occurring during the discharge stroke of the respective by=passed cylinder. Thus the by-passed refrigerant is not returned to the common suction line but passes directly to the intake of a working cylinder. With this arrangement, recirculation ofrefrigerant heated in the unloaded cylinder 49 is minimized and continued increase in the temperature of the cylinder 19 due to such recirculation is prevented.

It. will be obvious that any suitable control may be provided for opening and closing the valve 26 when by-passing of the cylinder I9 is desired and that the operation of the valve 26 in response to suction line pressure has been illustrated and described merely by way of example.

The refrigerant circuit described above effectively avoids the excessive heating which may occur in conventional practice wherein refrigerant from by-passed cylinders is returned to the common suction line so that a substantial portion thereof is returned to the by-passed cylinders and thereb effects an undesirable increase in the temperature of these cylinders.

What I claim as new and desire to secure by Letters Patent of the United States is:

1.14 refrigerant compressin apparatus adapted to be connected in a closed refrigerant circuit andcomprising a plurality of compressor cylinders each having an inlet and an outlet, an intake connection for said apparatus, a discharge connection for said apparatus, separate conduit means for connecting said intake connection respectively to each of said inlets, means for connecting said outlets of said cylinders to said discharge connection and for preventing reverse now of refrigerant therefrom to the outlet of one of said cylinders, conduit means connecting the outlet of said one of said cylinders to the inlet of .another of said cylinders at said other cylinder and remote from said intake connection, and means dependent upon a condition of operation of said apparatus for controlling said lastmentioned conduit means to effect unloading of said one cylinder and the discharge of refrigerant therefrom directly to the intake of said other cylinder, said apparatus including means for controlling the cycle of said one cylinder to effect discharge of refrigerant therefrom during the intake portion of the cycle of said other cylinder, whereby the hot compressed refrigerant .is directed preferentially to said other cylinder and the recirculation of refrigerant discharged from said one cylinder is minimized.

2. A refrigerant compressing apparatus adapted to be connected in a closed refrigerant circuit and comprising a plurality of compressor cylinders each having an inlet and an outlet, an intake connection for said apparatus,a discharge connection for said apparatus, a common intake conduit communicating at its ends with said inlets for said cylinders, means providing communication between said intake connection and said intake conduit intermediate the ends of said conduit, discharge conduits connecting the outlets of said cylinders and said discharge connection. conduit means including a normally closed valve and connecting the outlet of one of said cylinders with the inlet of another of said cylinders adjacent the corresponding end of said common conduit and remote from said intake connection, and means for openin said valve to effect unloading of said one. cylinder and the discharge of refrigerant therefrom directly to the intake of said other cylinder, said apparatus including means for controlling the cycle of said one cylinder to effect discharge of refrigerant therefrom during the intake portion of the cycle of. said other cylinder, whereby recirculation of refrigerant discharged from said one cylinder is minimized.

WAYNE E. DODSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,595,370 Watts Aug. 10, 1926 1,671,984 Goodman June 5, 1928 2,154,136 Parcaro Apr. 11, 1939 2,458,933 Dodson Jan. 11, 1949 

